Our long term goal is to determine the molecular structures of DNA-containing viruses such as P22 bacteriophage and herpes simplex virus type 1 capsid which have diameters of 600 E and 1,250 E, respectively. Our primary structural tool is electron cryomicroscopy and computer reconstruction and the resolution of the reconstruction is targeted to beyond 10 E. The electron imaging technique has an intrinsic inaccuracy of measuring the amplitudes of the structure factors due to the microscope instrumental factors. This proposal is aimed at using X-ray solution scattering to provide the scattering amplitudes of these viral capsids at a broad range of frequencies from 1/1000 to 1/10 E-1. These measurements will be used to correct those computed from the electron images of the corresponding capsids.